DEPENDENCE OF THE ADEQUACY OF MUSCLE-RELAXATION ON THE DEGREE OF NEUROMUSCULAR BLOCK AND DEPTH OF ENFLURANE ANESTHESIA DURING ABDOMINAL-SURGERY

We studied the intensity of neuromuscular block that is adequate for s urgical relaxation at different end-tidal levels of enflurane during N 2O-O-2-fentanyl anesthesia in 30 patients undergoing upper abdominal s urgery. After induction of anesthesia with thiopental 4-6 mg/kg and ve curonium 0.07 mg/kg intravenously (I.V.), patients were randomly assig ned to receive nitrous oxide-oxygen (2:1) and enflurane at 0.3% (Group I), 0.6% (Group II), or 1.2% (Group III) end-tidal level throughout a nesthesia. The initial neuromuscular block was allowed to terminate an d additional increments of 1 mg vecuronium were given when indicated b y clinical signs or by spontaneous electromyography of neck muscles. I n Group I additional vecuronium had to be given 62 times and in Groups Il and III, 33, and 16 times, respectively. The mean (so) neuromuscul ar block at the time of additional vecuronium was 75.8% +/- 20.7%, 62. 5% +/- 20.1%, and 39.3% +/- 21.1% in Groups I to III, respectively. We conclude that there was a clear linear relationship between the end-t idal concentration of enflurane and the degree of neuromuscular block necessary to produce adequate surgical muscle relaxation (P < 0.001).